Day after day, week after week, they continue to multiply. As one moral conundrum fades from the headlines, another takes its place. A particularly surreal one turned up last week - the case of the man from Albuquerque in New Mexico who accused his former girlfriend of the theft of his sperm. She had got pregnant when, as far as her boyfriend was aware, she was on the pill. Or so he says. The girlfriend countered that the sperm was a "gift" which he had voluntarily surrendered.

Then it was the turn of Jack Kevorkian, "Dr Death", to return to prominence, after he carried out euthanasia on one of his patients on US network television.

New riddles of sex, life and death confront us as never before. Before, an overarching moral framework seemed firmly in place. Now, we have all begun to acknowledge the impossibility of some of the questions facing us. The popularity of programmes such as Radio 4's The Moral Maze is a reminder that millions of Britons are now happy to tussle with arguments back and forth.

A clutch of government committees reviews guidelines on fertility, reproduction and genetics. Ethics has become a boom subject. In the words of Max Elstein, founder of the Institute of Medicine, Law and Bioethics at Manchester and Liverpool Universities, "It's greater than just multiplying. It's growing exponentially." Suddenly ethicists are everywhere.

The most obvious reason why ethical dilemmas (and ethicists) continue to multiply is technological change. The first test-tube baby was born only 20 years ago. Nobody at that time dreamed how fast dramatic new possibilities would continue to stack up: pensioner pregnancy, cloned organs as "spare parts" for patients, pig hearts and livers, the use of aborted foetal tissue as a cure for anything from Parkinson's disease to impotence. From Dolly the sheep to headless frogs, we are rapidly entering the kind of territory where even the most imaginative science-fiction writer might have blenched just a few years ago.

When the movie Jurassic Park was released, its tale of cloned dinosaurs still seemed to be projecting into the future. But the basic storyline - the creation of a large living creature from a small amount of DNA - now seems almost to be taken for granted. All these developments raise a similar question. As one churchman has put it: "To what degree can we fiddle with God's creation?"

FERTILITY AND babies provide one source of such dilemmas. In the old days, either you could have babies or you couldn't, and that was it. Now the menu of options is almost endless. Surrogate motherhood, embryo implantation, egg donation, sperm donation. Each brings with it a tangled set of potential dilemmas. On the one hand, there are the questions of consent and knowledge; on the other hand, the questions of what is perceived as "natural".

Genetic changes produce an obvious source of ethical anguish. Dolly the cloned sheep had people gasping in wonder and horror in equal numbers. The potential for human cloning lurks on a not so distant horizon. Does it matter? Should we care? Everybody has a view. The transplants of animal organs, too, offer a rich panoply of ethical questions. Pig hearts, pig livers - will we find ourselves mutating into some other kind of creature, like something in a Roald Dahl story?

Some decisions were always there to be taken - about who was owed what information, for example. But these decisions were taken by members of the medical profession alone. The questions raised by Dr Death, too, are based on the idea that doctors need a legal framework to take their most difficult decisions. In former times, doctors solved their own ethical dilemmas on the hoof; euthanasia, by any other name, happened behind closed doors.

The BMA produced its first handbook of medical ethics just 20 years ago. Even then, the tone was self-confident. It was 10 years ago that a hint of doubt crept in. Now hesitancy is itself the message. It is explicitly acknowledged, too, that "debate of ethical issues extends far beyond the medical profession". The boundaries are changing all the time. Thus the ethics committee is likely to propose a dramatic new change in the next few weeks that would turn the existing notion of presumed consent on its head. According to new proposals, those who do not wish their organs to be donated would have to carry cards; if you are not carrying a card, that would be taken as a form of consent.

All over the country new bodies have sprung up to grapple with previously invisible issues of what should be permitted when. Thus the Institute of Medicine, Law and Bioethics was established in 1995 "to shed light in difficult and controversial places". John Harris, professor of ethics at the institute, was in at the ground floor of the ethics business 30 years ago, having stumbled into it "by accident" when he published a thesis that explored the dilemmas which could be thrown up by the still-theoretical idea of organ transplants. Doctors came knocking on his door, seeking advice on all sorts of ethical matters. Overnight Professor Harris was perceived as an expert in the otherwise empty field.

None the less, Michael Wilks, the current chairman of the BMA's ethics committee, notes that there was much early caution. "The medical profession found it difficult to be removed from its god-like role," he says. Now, by contrast, there is an active desire to seek the views of ethicists.

And what is an ethicist? "An ethicist is somebody who says they know about ethics," is one succinct response from a leading figure in the field. Alternatively: "It's like with an expert - an expert is somebody who comes from out of town and wears glasses."

There is, however, respect for the intellectual rigour of the best in the field. One of the better known figures brought in to advise on ethical matters was the distinguished Oxford philosopher Mary Warnock. The committee that she chaired produced landmark recommendations on surrogacy and IVF, trying to disentangle the overlapping contradictions between choice and regulation.

Baroness Warnock is wary of what she regards as sloppy thinking in the ethics industry. "Philosophy teaches you the difference between an argument and something that isn't - or is a bad one. It teaches you to query your instincts, and to ask yourself: `Why?' " Her greatest worry is that, with the explosion of expertise, "most ethics committees are relatively superficial - a kind of orthodoxy is likely to creep up".

FOR THE church, religious input is crucial. It has its own committee on social responsibility - in effect, an ethics committee. Churchmen sit on almost every ethical committee in the country. Worries about being sidelined have gradually eased. In the words of one churchman: "A few years ago, there was a real fear that legislation on these difficult issues was based on pragmatism and the market rather than ethics. But that has changed."

Alastair Campbell, professor of medical ethics at Bristol University (another newly created chair), agrees with Baroness Warnock that moral philosophy is a key tool. "Common sense is all very fine, but it can be highly prejudiced. In the past doctors thought it was all a matter of experience and common sense. But it wasn't." Now, he believes, there has been a "dramatic change" in perception. "My medical colleagues welcome the possibility of another view."

The permanent ambiguity of ethical dilemmas is a constant theme in Campbell's teaching at Bristol. Try playing the ethics game for yourself, courtesy of a Bristol exam paper: "A woman is brain-dead, following a car crash. She is pregnant. Should she officiously be kept alive, to allow the baby to be born? If her husband also died in the crash, would that make a difference?"

You, too, can pronounce on ethical matters in the privacy of your own living-room or pub. Alternatively: there are plenty of professional vacancies out there. "Is there an ethicist in the house?" The demand will not diminish.